Just like in humans, when a dog tears a cranial cruciate ligament, surgery is needed to repair the injury. For dogs that weigh more than 40 pounds, the recommended treatment for a torn cranial cruciate ligament is a surgical procedure called a tibial plateau leveling osteotomy, commonly referred to as a TPLO. TPLO surgery involves removing the torn ligament, removing torn parts of the meniscus, and then cutting the lower leg bone (tibia) to rotate the surface of the bone that is involved in the knee joint. If you are wondering why the surgeon would have to cut a bone to repair a ligament, then you are not alone. A TPLO procedure uses the principles of basic physics to stabilize the knee. The dog knee joint is sloped, and the major force holding the joint in place is the cranial cruciate ligament. When the cranial cruciate ligament tears, a combination of the slope of the knee and muscles acting on the knee, including the quads and the calf muscles, causes the femur bone to slide forward when the dog bears weight on the leg. Each time this happens, it not only hurts, but it abnormally wears down the cartilage, resulting in the development of osteoarthritis. It can also tear the meniscus that cushions the dog knee joint. When the tibial bone is cut and rotated in a TPLO surgery, it levels out the knee joint and stabilizes the joint. This eliminates the sliding action that causes pain and arthritis. Of course, if a surgeon cuts a bone, then it must be repaired. After the bone is rotated, the surgeon installs a stainless steel bone plate with screws on the tibia to hold the two pieces in place.,Understanding the Canine Cruciate Ligament and TPLO Surgery